Control Flow (Python)

This module practices branching, looping, and sentinel-driven iteration.

Learning Metadata

• Difficulty: Beginner.
• Estimated Time: 20-35 minutes.
• Prerequisites: 01-foundations/types-and-io, 01-foundations/operators-and-expressions.
• Cross-Language Lens: Compare braces-and-loops in C++, C#, and Go with Python indentation while keeping the underlying branching logic identical.

Learning Outcomes

• FND-CFL-01: Select branches that cover normal and boundary conditions.
• FND-CFL-02: Write terminating loops and reason about their invariants.

Quick Run

Run from the repository root:

python scripts/automation.py run-module --module-path languages/python/01-foundations/control-flow

Topics Covered

• Conditional branches for FizzBuzz-style rules.
• For loops with clear termination conditions.
• While/for sentinel loops using stop value -1.
• Handling empty input sequences safely.

Common Pitfalls

• Not handling non-positive upper bounds before entering loops.
• Forgetting to stop on sentinel values in streaming input.
• Dividing by zero when no values were collected.

Cross-Language Notes

• In Python, read this module through the native focus ?Control Flow?; the shared folder name remains stable for side-by-side navigation.
• Use dynamic values, collection protocols, and context managers to demonstrate how to select branches that cover normal and boundary conditions.
• Compare observable behavior with the other tracks when learning to write terminating loops and reason about their invariants; equivalent evidence matters more than identical syntax.

Exercise Focus

• exercises/01.py: run FizzBuzz rules from 1 to N using condition priority.
• exercises/02.py: read integers until -1 and print average when values exist.

Exercise Specs

1. exercises/01.py

• Input: positive integer N.
• Output: sequence with Fizz, Buzz, or FizzBuzz substitutions.
• Edge cases: N <= 0; multiples of both 3 and 5.

2. exercises/02.py

• Input: integer stream terminated by -1.
• Output: average of entered values or a no-data message.
• Edge cases: first value already -1; negative values other than sentinel.

Check Your Work

Run from the repository root after implementing a starter:

python scripts/automation.py check-exercise --language python --level 01-foundations --module control-flow --exercise 01

Change --exercise 01 to --exercise 02 for the second task. Consult exercises/solutions/ only after making a complete attempt.

Checkpoint

• I can explain the core ideas of this module.
• I can run and modify example/main.py.
• I completed exercises/01.py.
• I completed exercises/02.py.
• I validated at least one edge case for each exercise.

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